title: Longitudinal analysis of peritoneal fluid transport and its determinants in a cohort of incident peritoneal dialysis patients.
abstract: OBJECTIVE
  There is a paucity of large longitudinal studies on the time course of peritoneal fluid transport. The aim of the present study was to longitudinally analyze changes in fluid transport and relevant solute transport parameters in patients treated with a conventional peritoneal dialysis (PD) fluid and, to mimic clinical reality, not selected for the presence or absence of ultrafiltration (UF) failure.
  
  
  METHODS
  This prospective single-center cohort study followed 138 consecutive incident PD patients from July 1994 until censoring in August 2004. The design was longitudinal, with repeated measures over time in each patient. Patients had undergone at least 1 and a maximum of 5 annual standard peritoneal permeability analyses (SPAs) using 3.86% glucose dialysate. A linear mixed model was used to analyze the longitudinal data.
  
  
  RESULTS
  No differences in patient characteristics were present at baseline in relation to the number of available SPAs. There were also no differences in patient withdrawal during the years of follow-up. A gradual decline in fluid transport, expressed as free water transport (FWT), small-pore fluid transport (SPFT), and transcapillary UF (TCUF), was observed with duration of PD. The decline was mainly attributable to patients who developed UF failure. The time courses for the determinants of fluid transport, such as the reflection coefficient (σ) and the UF coefficient (LpA), were not different. However, they were associated with an increase in the mass transfer area coefficient of creatinine, reflecting the peritoneal vascular surface area.
  
  
  CONCLUSIONS
  Fluid profiles for FWT and SPFT during a dwell can be explained by current knowledge of the three-pore model. Fluid transport declines with the duration of PD because of an increase in the vascular surface area, leading to a rapid dissipation of glucose as the osmotic agent. The absence of a trend in the time course of osmotic conductance and its constituents-that is, LpA and σ-suggests that, in an unselected population, these parameters are affected only late in the time course of PD.
authors.affiliation: Division of Nephrology, Department of Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.
authors.forename: Annemieke M
authors.initials: AM
authors.lastname: Coester
authors.forename: Watske
authors.initials: W
authors.lastname: Smit
authors.forename: Dirk G
authors.initials: DG
authors.lastname: Struijk
authors.forename: Alena
authors.initials: A
authors.lastname: Parikova
authors.forename: Raymond T
authors.initials: RT
authors.lastname: Krediet
mesh_terms: D000328:Adult; D000368:Aged; D001202:Ascitic Fluid / Q000378:metabolism*; D001692:Biological Transport; D015331:Cohort Studies; D015314:Dialysis Solutions; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000628:therapy*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D011446:Prospective Studies; D014462:Ultrafiltration / Q000379:methods; D014882:Water-Electrolyte Balance
chemical_list: D015314:Dialysis Solutions
keywords: Peritoneal fluid transport; free water transport: small-pore fluid transport; linear mixed model; prospective longitudinal study; standard peritoneal permeability analysis